Control system for clothes dryers



y 1964 T. P. FLEER ETAL 3,132,853

CONTROL SYSTEM FOR CLOTHES DRYERS Filed April 27, 1959 5 Sheets-Sheet 1 F l s. 3

F s. l

l V N T O R 5 5% as I28 BY H6 w a THEIR AGE LIT May 12., 1964 T. P. FLEER ETAL CONTROL SYSTEM FOR CLOTHES DRYERS Filed April 27, 1959 s Sheets-Sheet 2 THEIR AGENT y 1964 T. P. FLEER ETAL 3,132,853

CONTROL SYSTEM FOR CLOTHES DRYERS Filed April 27, 1959 a Sheets-Sheet :5

FIG. 4

THEIR Ag JE fi 3,132,853 CONTROL SYSTEM FOR CLOTHES DRYERS Thomas P. Fleer, Afiton, and Joseph Roos, Ferguson,

Mo., assignors, by mesne assignments, to White-Rodgers Company, a corporation of Missouri Filed Apr. 27, 1959, Ser. No. 809,281 Claims. (Cl. 263-33) This invention relates to control systems for clothes dryers and particularly to an automatic control system theretor wherein means responsive to the dryer exhaust temperature is employed in a novel arrangement; to automatically modulate the output of the dryer heat-producing means in a manner to achieve the shortest drying time for any load of wet clothing in any dryer consistent with an economical use of the fuel or energy being consumed while at the same time minimizing the risk of scorching or overheating the clothing; to automatically terminate operation of the heat-producing means when the clothing has attained the desired dryness; and to automatically effect a predetenr-ined cool-down period subsequent to termination of operation of the heat-producing means.

This application is a continuationin-part of our application Serial No. 795,831, filed February 26, 1959, now abandoned.

The primary object of the invention is to provide a gen erally new and improved control system for clothes dryers which is particularly simple and economical in construction and reliable and fully automatic in operation.

A further object is the provision of an automatic con trol device for clothes dryers which, upon initiation of a drying cycle; effects operation of the heat producer at a relatively high heat output rate unit the temperature of the dryer exhaust air has reached a first predetermined point which reflects an optimum drying rate for the dryer; then gradually reduces the output of the heat producer to a predetermined minimum as the dryer exhaust temperature continuously tends to rise above this point due to decreasing moisture in the clothing as drying progresses thereby to approach a constant drying rate throughout the major portion of the drying cycle; then maintains the predetermined heat output until the dryer exhaust temperature reaches a second predetermined higher temperature reflecting the desired dryness of the clothing; whereupon it operates to cut oil heat production.

A further more specific object is to provide automatic means for gradually throttling the cfuel supply to .the gas burner in a gas-fired clothes dryer from a maximum to a predetermined minimum flow as the dryer exhaust temperature continuously tends to rise above a. predator mined point as drying progresses, and to then cut off all flow of fuel to the burner when the dryer exhaust temperature reaches a second predetermined higher point under operation of the predetermined minimum flow.

A further object is the provision of an automatic control device for clothes dryers which, upon initiation of a drying cycle; effects operation of the dryer drum and the air-circulating means and efiects operation oi the heatproducing means at a high heat output rate; gradually reduces the heat output rate of the heat producer to a predetermined as the dryer exhaust temperature continuously tends to rise above a first predetermined point as drying progresses in a manner to the temperature rise of the dryer exhaust throughout the major portion of the drying cycle; completely cuts off heat production when the dryer exhaust temperature attains a second, higher, predetermined point under dryer operation on the predetermined minimum heat output; and stops operation of the dryer drum and air-circulating Lil means when the exhaust air temperature drops from said higher temperature to a predetermined lower temperature.

A further object is to provide means in an automatic control device of the above character by which the cutoff point of the heat producer is automatically varied in accordance with variations in the temperature of the air ambient to the dryer.

These and further objects and advantages of the invention will become apparent from the following description when read in connection with the accompanying drawings.

In the drawings:

FIG. '1 is a schematic view of a clothes dryer control system constructed in accordance with the present invention;

FIG. 2 is a longitudinal sectional view of the fuel supply control device for the dryer heat producer;

FIG. 3 is a detail view of the fuel flow modulating valve and is taken on line 33 of BIG. 2; and

FIG. 4 is a schematic view showing a modified arrangement of the circuit-holding means in the control system shown in FIG. 1.

Referring to FIG. 1 of the drawings the numeral 10 generally indicates a gas-fired clothes dryer having a clothing drum 12 mounted tor rotation on a shaft 14 and rollers 15, a heat-producing means in the :form of a burner 16, and an air-circulating blower 18. Heated air and the products of combustion from burner 16 are drawn into the clothing drum 12 at one point, [through the drum and out of the drum at another point, then outwardly of the dryer casing through an exhaust passage 20 by the circulator 18, as indicated by directional arrows. The rear wall 22 of the drum 12 is suitably perforated to permit free circulation therethrough. The drum 12 and circulating device 18 are provided with suitable pulleys 24 and 26 and are driven through a suitable belt or belts (not shown) by an electric motor, graphically indicated at 28.

Fuel is supplied to the burner 16 from a suitable source through a tuel supply line 29, and the flow of fuel to the burner is controlled by a fuel flow control device generally indicated at 30. The fuel fiow control device 30, shown in more detail in FIG. 2, consists of a body member 32 having an inlet passage 34, an outlet passage 36, and a connecting passage 38. A partition 40 separating inlet passage 34 from connecting passage 38 is provided with a port therethrough fitted with a Valve seat 42. A reciprocating poppet valve 44 cooperates with seat 42 to control the flow of fuel item the supply line to passage 38. The valve 44, which will be referred to as the cutoff valve, is normally held in a closed position by a spring 46, and it is moved to an open position, as shown in FIG. 2, by a. solenoid actuator 48 when it is energized. The solenoid actuator 48 includes a plunger guide sleeve 49, a slidably mounted plunger St} to which valve 44 is attached, a plunger stop member 53 of magnetic material, and a winding 52. The solenoid actuator 48 is suitably attached to body member 32.

The outlet passage 36 is formed in a hollow plug 54 threadedly engaged in a threaded opening 56 in the body member 32. The hollow plug 54 is provided with a sleeve portion 58 at the left end thereof which extends into connecting passage 38 and slidably receives a slide valve member 60. The sleeve portion 58 of hollow plug 54 is provided with longitudinal slots 62 in the wall thereof extending inwardly from its left end with which slide valve 60 cooperates to vary the flow of fuel from the connecting passage 38 to the outlet passage 36. The slide valve 60 is biased outwardly with respect to sleeve portion 58 by a spring 64..

A second hollow plug 66 threadedly received in the threaded passage 56 has a sleeve portion 68 extending exteriorly of the body member 32 and forming a fuel conduit leading (from the body member to the base of burner 16. The outer end of sleeve portion 68 is internally threaded and fitted with a threaded orifice plug 70- having a calibrated orifice therein. The burner 16 is mounted on the body member 32 by means of mounting brackets 72 and screws 74.

A bore 73 extending from passageway 38 and a tube 75 leading to the base of burner 16 at a point near the orifice plug 70 provide a fuel passage which permits a predetermined minimum flow of fuel to burner 16 when slide valve 60 is in its innermost position so as to cut off all fuel flow through the slots 62 in sleeve 58. The tube 75 is provided at its end with a second orifice plug 7'7 having a calibrated orifice therein. The reason for providing a separate fuel passage 73-75 leading from passage 38 to the burner base with a separate fuel metering orifice at the end thereof to permit the minimum flow to the burner, in lieu of merely providing a small hole or groove in slide valve 60 or in sleeve 58 for this purpose, is to maintain a substantially constant velocity of flow through the metering orifice which is passing the minimum flow. It will be appreciated that as the slide valve 6t? is moved inwardly to reduce the communication between passage 38 and outlet passage 36, the pressure drop in passage 36 will be considerable and the velocity through the orifice in plug 70 will consequently be reduced considerably.

The turn-down or throttling limit at which a gas burner will operate satisfactorily is considerably reduced if, at the same time the flow is being reduced, the velocity through the burner orifice is also reduced. This is so because, as throttling progresses, the fuel stream through the orifice reaches a point wherein its kinetic energy becomes insufiicient to aspirate adequate primary air for combustion, and to carry the mixture of gas and air at a sufiicient speed on through the burner tube to the burner head where combustion is intended to occur. When the mixture velocity drops below the speed of flame propagation, the flame retreats from the burner head back to the fuel orifice where it burns entirely on secondary air. It will be appreciated, therefore, from the foregoing that the provision of the auxiliary fuel passage 7375 and the auxiliary orifice in plug 77 plays an important role in rendering applicants device more universally adaptable.

Mounted on a wall of connecting passage 38 is an expansible chamber, generally indicated at 76, comprising a flexible inner wall or diaphragm '78 and a rigid outer wall 80. A bulb 82 mounted in a position so as to be sensitive to the dryer exhaust temperature communicates with a space between the flexible and rigid walls of the expansible chamber through a length of capillary tubing 84. The bulb 82, the capillary 84, and the expansible chamber form a sealed system filled with a thermally expanding liquid such as xylene. Pivotally mounted in a wall of the connecting passage 38 on a pivot 86 is a lever 88 having a long arm 90 which carries at its free end a threadedly adjustable contact member 92, the right end of which engages the outer end of the slide valve 69. The lever 88 also has a short arm 94 which is engaged at its free end by one end of a push rod 96 slidably mounted in a support member 98. The other end of the push rod 96 is biased against the flexible wall 78 of the expansible chamber by a spring 101) so that, when the fluid in bulb 32 exapnds, the lever 88 is rotated counterclockwise on its pivot 86 and the sleeve valve 60 is moved inwardly with respect to sleeve portion 53.

A bellows 93 attached at one end of the left end of the threadedly adjustable contact member 92 eagages at its other end the right end of a push rod 102 which is slidably mounted in a wall of passage 38 and extends exteriorly of the body member 32. The push rod 102 is normally biased against the end of the bellows 93 by a spring 104, and the opening in the wall in which push rod 102 is slidably mounted is provided with a pliable O-ring seal 196. Mounted exteriorly on the body member 32 on an adjustable mounting bracket 1&8 snap-action switching device 110 having an operating pin 112 arranged to be engaged by the exteriorly projecting left end of push rod 102. The bellows 93, interposed between the contact member 92 and push rod 1632, is filled with athermally expansible liquid which expands and contracts inresponse to ambient temperature changes to Vary the operative connection between the end of arm and switch 110.

The switch 110, as shown diagrammatically in FIG. 1, is indicated as having a solid line position and a dotted line position, between which positions it is operated through the lever 88, bellows 93, and push rod 102 as a result of expansion and contraction of the liquid in temperature sensitive bulb 82. The solid line position of switch may be regarded as its cold position, that is; the position to which it is operated when the temperature affecting bulb 82 drops below a predetermined point, while the dotted line position may be regarded as the hot position or the position to which the switch is operated when the temperature affecting bulb 82 exceeds a predetermined point. The switch 110 may further include means well known and understood in the art, such as a variable lost-motion connection in the switch operating linkage whereby a greater or lesser difiference between predetermined high and predetermined low temperatures is required to effect operation of the switch from one position to the other. The temperature at which switch 110 is operated from its cold, solid line position to its hot, dotted line position, or conversely, may be manually varied by adjustably positioning the switch closer or farther away from the body member on its adjustable bracket 108, which is provided with slotted holes 169 to receive attaching screws 114.

- The electrical portion of the system, shown in FIG. 1,

includes as primary elements; a pair of terminals 116 and 118 for connection with a suitable source of electrical power, a spring-returned, push-button switch 120, a relay 122, the motor 28, the switch 110, the winding 52 of the solenoid valve actuator 48, a resistor 124, and a line switch 126. When line switch 126 and push-button switch 120 are closed, the relay is energized through a circuit which may be traced as follows: from terminal 116 through a lead128, the line switch 126, a lead 130, a lead 132. push-button switch 120, a lead 134, the winding of relay 122, and a lead 136 to opposite terminal 118. When relay 122 is energized its contacts 123-125 are bridged, thereby completing a holding circuit to maintain its own energization after the push-button switch 120 is released and also thereby completing circuits for energization of the driving motor 28 and the solenoid actuator winding 52.

The holding circuit for relay 122, completed through the now-closed contacts 123-125, may be traced as follows:

from terminal 116 through lead 128, through line switch 126, lead 130, a lead 131, relay contacts 123-125, a lead 133, a lead 148, double-throw switch 110 when in its cold, solid line position, a lead 142, a lead 144, resistor 124, relay winding 122, and lead 136 to terminal 118.

The energizing circuit for motor 28, completed upon energizing of relay 122, may be traced as foilows: from terminal 116 through lead 128, line switch 126, lead 130,

lead 131, relay contacts 123-125, lead 138, lead 146, thewinding of motor 23, a lead 148, and a lead 136 to terminal 118. I

The energizing circuit for solenoid valve actuator winding 52, which is completed upon energization of relay 122, may be traced as follows: from terminal 116 through lead 128, line switch 126, lead 130, a lead 131, relay contacts 123-125, lead 138, lead 140, switch 110 in its cold, solid line position, lead 142, lead 144, winding 52, a lead 150, and lead 136 to terminal 118.

When the dryer exhaust temperature to which bulb 82 is sensitive reaches a predetermined point switch 110 is operated to its hot, dotted line position. This action breaks the described holding circuit for relay 122 and is a double-throw, single-pole,

the energizing circuit for solenoid actuator winding 52, which were completed through the solid line position of switch 110. The described circuit for energizing motor 28 was also broken at relay contacts 123-125 when the relay holding circuit was broken, but a second energizing circuit for motor 28 is completed when switch 110 is moved to its hot, dotted line position. This motor circuit may be traced from terminal 116 through lead 128, line switch 126, a lead 152, switch 110 in its hot, dotted line position, lead 140, lead 146, windings of motor 28, lead 148, and lead 136 to terminal 118.

In the modification shown in FIG. 4 of the drawings, the holding relay 122 is dispensed with and a normally open switch 154, arranged to be actuated to a closed position by the solenoid 48 when energized, is substituted therefor to maintain energization of the motor winding and solenoid winding after the push-button starting switch is released. All elements in the modification shown in FIG. 4 which are identical to those in FIGS. 1, 2, and 3 are similarly designated. The normally open switch 154 in FIG. 4 may be arranged to be closed by engagement of an upward extension of the solenoid plunger extending through a bore through the plunger stop 53, or the switch arm 154 maybe arranged to be attracted to the magnetic plunger stop member 53 thereby to close the switch upon energization of the solenoid winding.

' When in FIG. 4 the line switch 126 is closed and the push button 120 is depressed to initiate a drying cycle, the solenoid winding 52 is energized through a circuit which may be traced as follows: from terminal 116, through lead 128, line switch 126, a lead 156, lead 158, push-button switch 120, a lead 160, lead 162, the winding 52, and a lead 164 to opposite terminal 118. When winding 52 is energized the switch 154 is closed, thereby completing a holding circuit for winding 52 around the push-button switch 120 and thereby completing a circuit for energization of motor 28. The holding circuit for solenoid winding 52 may be traced as follows: from terminal 116, through lead 128, switch126, lead 156, switch 154, a lead 166, a lead 168, switch 118 in a solid line position, a lead 179, the resistor 124, a lead 172, lead 162, winding 52, and lead 164 to terminal 118. The circuit through switch 154 for energizing motor 28 may be traced as follows: from terminal 116 through lead 128, switch 126, lead 156, switch 154, lead 166, a lead 174, motor 28, a lead 176, and a lead 164 to terminal 118.

When in FIG. 4 the dryer exhaust temperature reaches a predetermined point, switch 110 is operated to its hot, dotted line position. This action breaks the described holding circuit for solenoid winding 52, which was completed through the solid line position of switch 118, and consequently eifects the breaking of the described circuit for motor 28 which was completed through switch 154. I A second circuit for maintaining operation of motor 28 is completed, however, when switch 110 moves to its hot, dotted line position. This motor circuit may be traced from terminal 116 through lead 128, line switch 126, lead 156, a lead 178, switch 110 in its hot, dotted line position, lead 168, lead 174, motor 28, lead 176, and lead 164 to terminal 118.

Operation When the dryer exhaust temperature to which bulb 82 is sensitive is at or below a predetermined cool-down temperature switch 110 will be in its solid line position and slide valve 61) will be in its outermost position in solenoid winding 52 through the described circuit. The energization of relay 122 in FIG. 1 and the closing of its contacts 123-125 completes the described holding circuit for the relay 122 and the described energizing circuit for motor 28 and solenoid winding 52. The energization of solenoid winding 52 in FIG. 4 and the consequent closing of switch 154 completes a holding circuit for the solenoid winding and a circuit for the energization of driving motor 28. In both modifications energization of the motor 28 starts rotation of the dryer drum 12 and the circulating device 18, and energization of solenoid actuator winding 52 effects the opening of normally closed valve 44.

Fuelnow flows to the burner 16 at a maximum rate where it is ignited by any suitable ignition means (not shown). Initially the dryer exhaust temperature rises rapidly under maximum burner operation from some considerably lower ambient room temperature to a first, predetermined temperature. As the dryer exhaust temperature tends to increase above this first predetermined temperature, expansion of the liquid in bulb 82 through the means described moves the slide valve 60 inwardly to reduce the flow of fuel to the burner in a manner to limit the rise in the dryer exhaust temperature above this first, predetermined temperature. As drying progresses and the moisture content of the clothing is gradually reduced, the tendency of the dryer exhaust temperature to rise will persist, due to the fact that less and less.

heat input will be required to maintain this first, predetermined temperature, and the sensitive bulb 82 will continue to respond and gradually further reduce the flow of fuel until a maximum turn-down or throttling point is reached, whereafter a fixed minimum flow of fuel will be supplied through passage 73-75 and consequently a fixed minimum main burner heatoutput will maintain.

Under the condition of fixed minimum heat output, the dryer exhaust temperature is now permitted to rise, but it will, of course,rise at a slower rate than it would at some higher burner heat output rate. When the increasing dryer exhaust temperature reaches a second, predetermined temperature when operating at the minimum heat output rate, the expansion of the liquid in bulb 82 will have progressed to a point wherein actuation of switch from its cold, solid line position to its hot, dotted line position will be effected. This action will effect de-energization of solenoid actuator Winding 52 to cut oil burner operation and will break the first-established driving motor circuit in both FIGS. 1 and. 4, but the driving motor 28 will continue to be operated through the second-described motor circuits in FIGS. 1 and 4, which are completed through switch 110 in its dotted line position. The drum 12 and circulator 18 will, therefore, continue to operate after heat production is stopped.

With the burner in an inoperative condition the now dry clothing in drum 12 will be cooled by the circulation of unheated air and the dryer exhaust temperature will decrease. When the dryer exhaust temperature decreases to a predetermined, cool-down point, the switch 110 will be operated back to its solid line position. This operation of switch 110 now breaks the second circuit for driving motor 28 in both FIGS. 1 and 4, and the drying cycle is completed. It is to be understood that the operating differential of switch 110 and its response are such that a substantial cooling of the clothing is effected before the switch 110 is actuated back to its solid .line position.

The purpose of resistor 124 is to prevent the pull-in of relay 122 in FIG. 1 or solenoid actuator 48 in FIG. 4 at the termination of the cool-down period when switch 110 is actuated back to its solid line position. The momentum of motor 28 and the members it drives will efiect some generation of electrical energy by the motor which may, under certain conditions, be suflicient to eifect a pull-in of relay 122 or the solenoid actuator 48, both of which are, under these conditions, in a closed circuit with the motor 28. The resistor 124 is of such value as to reduce the flow of current through relay winding 122 or solenoid winding 52 from the regular power source to a point which, while sufficient to hold relay 22 or solenoid 48 in an energized position once they have been moved to this position by full energization through the initiating push-button circuit, is yet insufiicient to move the relay contacts closed from an open position or the solenoid valve open from a closed position.

When the dryer is operating at a fixed minimum heat output near the end of a drying cycle, variations in the temperature of the air ambient to the dryer will have a relatively marked effect upon the temperature of the dryer exhaust. If the system is calibrated to cut oii heat production when the dryer exhaust temperature has risen to a point which reflects a desired condition of dryness of the clothing under operation in an ambient temperature of say 70 Fahrenheit, this point of dryer exhaust temperature may never be reached if the temperature ambient to the dryer is say 40 Fahrenheit even though the desired dryness of the clothing has been attained. On the other hand, if the ambient temperature is 160 Fahrenheit instead of 70 Fahrenheit, the dryer exhaust temperature will reach the burner cut-off point before the desired dryness of the clothing has been attained. The temperature responsive bellows 93 interposed between the free end of lever arm 90 and operating push rod 102, being responsive to ambient temperature, operates to cut off heat production at a lower dryer exhaust temperature under operating conditions in a low ambient temperature and at a higher dryer exhaust temperature under operating conditions in a higher ambient temperature. The cut-oh? point may also be varied manually by loosening the screws 114 and shifting the switch 114) left or right, in FIG. 2.

i The foregoing description is intended to be illustrative and not limiting, the scope of the invention being set forth in the appended claims.

We claim:

1. In a clothes dryer in combination, a drying drum, a variable output heat producer, means including an inlet duct leading to said drum and an exhaust duct leading therefrom for circulating air heated by said heat producer through said drying drum and thereafter exhausting it, a two-position control device for said heat producer having a first position which permits operation of said heat producer and a second position in which operation of said heat producer is prevented, said control device being normally biased in its first position, a second control means for gradually varying the output of said heat producer between its maximum capacity output and a predetermined minimum output, a temperature responsive actuator including a temperature sensing bulb positioned in said exhaust duct, said actuator. being operatively connected to said second control means and being operative to gradually reduce the output of said heat producer as the dryer exhaust air temperature tends to increase above a first predetermined temperature until the output of said heat producer is reduced to said predetermined minimum, and means forming an operative connection between said temperature responsive actuator and said two position control device which is operative to effect the movement of said control device from its first position to its second position when said actuator responds to a second, predetermined, higher, exhaust, air temperature.

2. In a clothes dryer in combination, a rotatable drying drum, a variable output heat producer, an electrically operated on and 011 control device for controlling operation of said heat producer and being operative when energized to effect operation of said heat producer and when de-energized to cut off its operation, means including a blower for circulating air heated by said heat producer through said drying drum and thereafter exhausting it, an electric motor for driving said drum and said blower, movable means for varying the heat output of said heat producer between maximum output and a predetermined minimum output, a temperature responsive device operatively connected to said movable means and being responsive to increasing temperature of the dryer exhaust air above a first predetermined temperature to reduce the output of said heat producer, an electrical relay having normally open contacts, a normally open push-button switch, a double-throw switching device having a cold position and a hot position, electrical circuit means completed through said push button when closed for energizing said relay, electrical circuit means completed through said relay contacts when closed for energizing said driving motor, electrical circuit means completed through said relay contacts when closed and through said double-throw switch when in a cold position for energizing said electrically operated control means and for maintaining energization of said relay when said push button is released, additional electrical circuit means independent of said relay contacts and completed through said double-throw switch when in its hot position for energizing said driving motor, and said temperature responsive means being operatively connected to said double-throw switch and being arranged to effect the operation of said switch from its cold to hot position when said temperature responsive means responds to a second predetermined higher exhaust air temperature, whereby said heat producer is rendered inoperative while said drum and circulating blower are maintained operative, and said temperature responsive means being operative to eflect the return of said doublethrow switch to its cold position when subsequently responding to a predetermined decrease in temperature from said predetermined higher temperature thereby to render said driving motor inoperative.

3. In a clothes dryer control, a variable output heat producer, a two-position control device for said heat producer having a cold position which permits operation of said heat producer and a hot position which prevents operation of said heat producer, a second control means for varying the output of said heat producer, a temperature responsive actuator operatively connected to said second control means and being responsive to the temperature of a space being heated by said heat producer to reduce the heat output of said heat producer as the temperature of the space being heated tends to rise above a first predetermined temperature, means forming an operative connection between said temperature responsive actuator and said two-position control device, and said temperature responsive actuator being responsive to a second higher temperature of the space being heated to effect the movement of said two-position control device from its cold to its hot position thereby to cut oif operation of said heat producer, and said operative connection including a temperature responsive device responsive to the temperature ambient to the space being heated by said heat producer and operative to effect the movement of said two-position control device by said temperature responsive actuator from hot to cold position at a lower heated space temperature when the temperature ambient to the heated space decreases.

4. In a control system for a clothes dryer, a variable output heat producer, an electrically operated on or ofi control device for controlling operation of said heat producer and being operative when energized to effect operation of said heat producer and when de energized to render it inoperative, movable means for varying the heat output of said heat producer, temperature responsive means operatively connected to said movable means and being responsive to variations in the temperature of a body being heated by said heat producer to vary the output of said heat producer, a normally open circuit holding switch operatively associated with said on or ofi control device and arranged to close upon energization of said on or o control device, a normally closed cut-otr' switch, a normally open push-button starting switch, electrical circuit means for energizing said on or off control device including said push-button starting switch in a closed position, a holding circuit for maintaining energization of said on or on control device when said push-button starting switch is released including said circuit holding switch in a closed position and said cut-off switch in a closed position, and means forming an operative connection between said temperature responsive device and said normally closed cut-off switch to effect the opening thereof when said temperature responsive device moves a predetermined amount in one direction in response to increasing temperature.

5. In a control system for a clothes dryer, a variable output heat producer, an electrically operated on or off control device for said heat producer being operative when energized to effect operation of said heat producer and when de-energized to render it inoperative, movable means for varying the heat output of said heat producer between a relatively larger output and a minimum output and being biased in a position to eflfect a relatively large output, temperature responsive means operatively connected to said movable means and being responsive to a rise in the temperature of a body being heated by said heat producer to reduce the output of said heat producer, a normally open circuit holding switch operatively associated with said on or oil control device and arranged to be closed thereby upon energization thereof, a normally closed cut-off switch, a normally open push-button starting switch, electrical circuit means for energizing said on or o control device including said push-button switch when closed, a holding circuit for maintaining energization of said on or ofi control device when said push-button starting switch is released including said holding switch when closed and said cut-on switch when closed, and means forming a connection between said temperature responsive device and said cut-ofi switch operative to effect the opening of said cut-oil switch when the temperature to which said temperature responsive device is sensitive increases a predetermined amount beyond that point at which minimum output of the heat producer is efiected.

6. In a clothes dryer in combination, a rotatable drying drum, a heat producer, an electrically operated control device for said heat producer which when energized effects its operation and when de-energized renders it inoperative, means including a blower for circulating air heated by said heat producer through said drying drum and then exhausting it, an electric motor for driving said drum and said blower, a normally open circuit-holding switch operatively associated with said control device and arranged to be closed thereby upon energization thereof, a double-throw switch having a hot position and a cold position, a normally open push-button starting switch, electrical circuit means completed through said push-button starting switch for energizing said control device, a holding circuit for maintaining energization of said control device when said push-button starting switch is released completed through said holding switch and said double-throw switch in a cold position, electrical circuit means for energizing said electric motor completed through said holding switch and said double-throw switch in a cold position, additional circuit means for energizing said electric motor completed through said double-throw switch in its hot position, and a temperature responsive actuator operatively connected to said double-throw switch and being operative in response to a perdetermined high temperature of the dryer exhaust to move said double-throw switch from its cold to its hot position thereby breaking said holding circuit and rendering said heat producer inoperative while retaining operation of said electric motor through said double-throw switch in its hot position, and being operative in response to a subsequent predetermined decrease in the temperature of the dryer exhaust to return said double-throw switch to its 10 cold position thereby to cut oil operation of said electric motor.

7. A clothes dryer as claimed in claim 6 which further includes temperature responsive means responsive to the temperature ambient to the dryer and interposed between said temperature responsive actuator and said double-throw switch and arranged to efiect the operation of said double-throw switch from-its cold to its hot position at lower dryer exhaust temperatures with decreasing ambient temperatures.

8. In a clothes dryer in combination, a rotatable drying drum, a heat producer, an electrically operated control device for said heat producer which when energized efiects its operation and when de-energized renders it inoperative, means including a blower for circulating air heated by said heat producer through said drying drum and then exhausting it, an electric motor for driving said drum and said blower, a normally open electrically operated switch which when energized closes, a double/throw switch having a hot position and a cold position, a nor mally open push-button starting switch, electrical circuit means completed through said push-button starting switch for energizing said electrically operated switch, a holding circuit for maintaining energization of said electrically operated switch when said push button is released completed through said electrically operated switch and said double-throw switch in its cold position, electrical circuit means for energizing said control device and said electric motor completed through said electrically operated switch and said double-throw switch in its cold position, additional circuit means for energizing said electric motor completed through said double-throw switch in its hot position, a temperature responsive actuator operatively connected to said double-throw switch and being operative in response to a predetermined high temperature of the dryer exhaust to move said double-throw switch from its cold to its hot position thereby breaking said holding circuit and cutting ofi heat production while maintaining operation of said driving motor through said double-throw switch in its hot position, and being operative in response to a subsequent predetermined decrease in the temperature of the dryer exhaust to return said double-throw switch to its cold position thereby cutting 01f operation of said motor, and temperature responsive means responsive to the temperature ambient to the dryer and operative to vary the operative connection between said temperature responsive actuator and said double-throw switch in a manner to effect the operation of said double-throw switch from its cold to hot position at lower dryer exhaust temperatures with decreasing ambient temperatures.

9. In a clothes dryer control, a heat producer, a controller having a cold position which permits operation of said heat producer and a hot position which cuts off operation of the heat producer, a first temperature responsive device operatively connected to said controller and responsive to a predetermined increase in the temperature of a portion of the dryer being heated by the burner above the temperature ambient to the dryer to move said controller from its cold to hot position, and a second temperature responsive device operatively associated with said first temperature responsive device and being operative in response to a decrease in the temperature ambient to the clothes dryer to cause said first temperature responsive device to move said controller from its cold to hot position in response to less than said predetermined increase in the temperature of the space being heated.

10. In a clothes dryer, a drying drum, means including said drying drum defining an air flow passageway which further includes an inlet portion leading to said drum and an exhaust portion leading therefrom, a gas burner in said inlet portion and a blower in said exhaust portion, a fuel supply conduit leading to said burner, a first normally closed electromagnetically opened valve in said conduit, a second normally open throttling valve in said conduit posterior to said first valve, a temperature 1 l responsive actuator including a temperature sensing bulb positioned in said exhaust portion thereby to respond to changes in the exhaust air temperature, said temperature responsive actuator being operative to gradually move said throttling valve toward a closed position as the exhaust air temperature tends to. rise above a first predetermined temperature, bypass means providing a predetermined minirnum flow of fuel to said burner when said throttling valve is moved to a closed position, an energizing circuit for said electromagnetic cutoff valve including a normally closed switch, and means forming an operative connection between said temperature responsive actu ator and said switch through which said actuator is operative to etfect the opening of said switch when the dryer exhaust temperature attains a second, higher, predetermined temperature. I

References Cited in the file of this patent UNITED STATES PATENTS Beach Nov. 5, Adams et a1. Jan. 2, Lenpo-ld Feb. 19, Bottom Jan. 15, Geldhof et al. May 18, Engel Sept. 20, Grayson Apr. 10, Matthews Oct. 23, Weber et a1 Nov. 4, Hullar Jan. 6, Hughes Mar. 24, Matthews Dec. 15, Hajny Feb. 9, 

1. IN A CLOTHES DRYER IN COMBINATION, A DRYING DRUM, A VARIABLE OUTPUT HEAT PRODUCER, MEANS INCLUDING AN INLET DUCT LEADING TO SAID DRUM AND AN EXHAUST DUCT LEADING THEREFROM FOR CIRCULATING AIR HEATED BY SAID HEAT PRODUCER THROUGH SAID DRYING DRUM THEREAFTER EXHAUSTING IT, A TWO-POSITION CONTROL DEVICE FOR SAID HEAT PRODUCER HAVING A FIRST POSITION WHICH PERMITS OPERATION OF SAID HEAT PRODUCER AND A SECOND POSITION IN WHICH OPERATION OF SAID HEAT PRODUCER IS PREVENTED, SAID CONTROL DEVICE BEING NORMALLY BIASED IN ITS FIRST POSITION, A SECOND CONTROL MEANS FOR GRADUALLY VARYING THE OUTPUT OF SAID HEAT PRODUCER BETWEEN ITS MAXIMUM CAPACITY OUTPUT AND A PREDETERMINED MINIMUM OUTPUT, A TEMPERATURE RESPONSIVE ACTUATOR INCLUDING A TEMPERATURE SENSING BULB POSITIONED IN SAID EXHAUST DUCT, SAID ACTUATOR BEING OPERATIVELY CONNECTED TO SAID SECOND CONTROL MEANS AND BEING OPERATIVE TO GRADUALLY REDUCE THE OUTPUT OF SAID HEAT PRODUCER AS THE DRYER EXHAUST AIR TEMPERATURE TENDS TO INCREASE ABOVE A FIRST PREDETERMINED TEMPERATURE UNTIL THE OUTPUT OF SAID HEAT PRODUCER IS REDUCED TO SAID PREDETERMINED MINIMUM, AND MEANS FORMING AN OPERATIVE CONNECTION BETWEEN SAID TEMPERATURE RESPONSIVE ACTUATOR AND SAID TWO POSITION CONTROL DEVICE WHICH IS OPERATIVE TO EFFECT THE MOVEMENT OF SAID CONTROL DEVICE FROM ITS FIRST POSITION TO ITS SECOND POSITION WHEN SAID ACTUATOR RESPONDS TO A SECOND, PREDETERMINED, HIGHER, EXHAUST, AIR TEMPERATURE. 